1. Field of the Invention
This invention relates to a process for homogeneously hydrogenating nitriles to primary amines under mild conditions utilizing anionic Group VIII metal hydride compositions as catalysts.
2. Brief Description of the Prior Art
The reduction of nitriles is an extremely important industrial process for the production of useful primary amines. For example, adiponitrile is industrially hydrogenated under heterogeneous conditions to yield hexamethylene diamine, which is a well known intermediate in the manufacture of nylon-66 and nylon-610.
Despite the fact that many different processes for the hydrogenation of nitriles are well known and industrially utilized these processes possess certain attendant disadvantages. For example, the references: J. Am. Chem. Soc., 66 pp. 725-731 (1944); U.S. Pat. No. 3,454,644 (1969); Ger. Offen. 2,052,730 (1971); Ger. Offen. 2,062,425 (1971); and U.S. Pat. No. 3,152,184 (1964) describe catalyzed processes either that require process temperatures above 150.degree. C. or reaction pressures above 150 psig of hydrogen gas in order to achieve adequate yields of primary amines therefrom. These process requirements lead to the disadvantages of the need for expensive apparatus and present special process hazards and require increased energy inputs.
Another process described in J. Am. Chem. Soc., 82, pp. 2386-2389 (1960) which involves low pressure catalytic hydrogenation, requires the presence of significant amounts of ammonia gas during the process to inhibit the formation of secondary amines, thus increasing the overall cost of such process.
The use of nickel clusters as catalysts is described in J. Am. Chem. Soc., 99 pp. 7380-7381 (1977) for reducing nitriles, such as acetonitrile, to amines. However, usually several reduction products are obtained which lowers the yield of the desired amine and presents purification problems.
Due to the large technical and industrial importance of amines, new and improved methods for their manufacture, including that of reduction of nitriles, are constantly being developed. What is desired in the technology of hydrogenating nitriles, is a process which does not require high temperatures, i.e., above 150.degree. C., high pressures, i.e. above 5-7 atmospheres, and which does not require the presence of ammonia for suppression of secondary and tertiary amine formation.